1. Field of the Invention
The field of the invention is that of seismic data acquisition. More specifically, the invention relates to the design of the insertion tips with which seismic sensors are provided, in order to allow them to be installed and/or held in the ground.
The invention relates in particular to the industry of oil prospecting using the seismic method in a land-based environment, but may be applied to any field which uses a seismic data acquisition network.
2. Background of the Invention
The operations of acquiring seismic data on land conventionally use networks of electronic control units to which there are connected sensors for detecting movements of the ground. Sensors of this type, known as geophones, are generally interconnected as a group of sensors via cables so as to form clusters known as “strings”. One or more of these strings are connected to said electronic control unit. The electronic control units, interconnected to one another by a wired digital network, or via a radio network, carry out the analogue/digital conversion of the signal from the groups of sensors and transmit these data to the recording truck via said digital network.
The lower face of the sensors is equipped with means for mechanical coupling to the ground. Depending on the nature of the land and/or the type of sensor, these mechanical coupling means may be a tip or a foot which is designed to be inserted into the ground.
In the case of tips, work has been carried out on the design thereof, and in particular on the length thereof, and it has been found that the longer the tip, the easier it is to insert it into the ground (knowing that these are traditionally pushed in by an operator's foot).
In parallel, new systems have recently been brought onto the market in which the sensors are annexed to the electronic conversion unit, which has the effect of eliminating the strings used with the geophones.
Sensors of this type are generally known as “digital sensors”.
According to one or the other of the sensor techniques, in order to gather the geophysical data, one or more seismic sources in contact with the ground are activated so as to propagate omnidirectional seismic wave trains. The sources may include explosives, weight drops or vibrating devices.
The wave trains reflected by the layers of the ground are detected by the sensors, which generate a signal characteristic of the reflection of the waves at the geological interfaces below ground.
It will therefore be understood that one important parameter for the precision of the geophysical data gathered is the coupling of the sensors to the ground, and more specifically the coupling of the tip to the ground.